Seth Gordon wrote:
Functors are a generalization from lists to things that can be mapped
over in general, and then monads are a generalization of functors.
Way to go! That way lies true co/monadic enlightenment. Put another way,
monads are no more about (only) IO/sequencing than fmap is
Kim-Ee Yeoh wrote:
Seth Gordon wrote:
Functors are a generalization from lists to things that can be mapped
over in general, and then monads are a generalization of functors.
Way to go! That way lies true co/monadic enlightenment.
I feel like I still don't understand comonads. Maybe I
On 8/1/07, Jeff Polakow [EMAIL PROTECTED] wrote:
But what about an actual object of type 'IO
Int', say?
I usually describe the type resulting from applying a monad a computation.
Same here. If m is a monad, then m a is a computation. (Of course,
computations are first-class values, like
On Thursday 02 August 2007 15:57, ok wrote:
It all depends on what you mean make sense to.
I can tell my student that (an instance of Monad) is a type constructor
applications of which support certain operations that must satisfy
certain operations. They can memorise that. But it remains
On 02/08/07, Alexis Hazell [EMAIL PROTECTED] wrote:
It's at this point that i feel there's an issue. Haskell Monads are used FOR
many many things. And rather than get to the core of what a Monad is, many
people provide two or three motivating examples - examples which merely serve
to show
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of peterv
However, one thing which I find annoying is that a classic
pure function cannot evaluate an IO function unless you use
unsafePerformIO; one must promote (?demote) the pure
function into the IO monad.
That's just a
On 8/2/07, Dougal Stanton [EMAIL PROTECTED] wrote:
Do I have an suggestions? Well, maybe the right way would be to do as
we do with map and fold, etc: show the explicitly recursive example,
then generalise. So, show how we could we would thread state in
Haskell, or how we would do optional
Ok,
I am guessing that if you were Neo in The Matrix, you would have taken
the Blue Pill. Blue Pill people ask How.
I suspect most people attracted to Haskell have already taken the Red
Pill. Red Pill people ask Why.
It is compulsion, not self-interest, that drives Red Pill people to look
This is about to put a definition/description to test. So please cooperate!
;)
Is this a useful – sufficient, not complete – definition/description for a
monad; for an imperative mind: (?)
A monad is like a loop that can run a new function against it's variable in
each iteration.
(I insist on
On Wednesday 01 August 2007 17:02, Kaveh Shahbazian wrote:
This is about to put a definition/description to test. So please cooperate!
;)
Is this a useful – sufficient, not complete – definition/description for a
monad; for an imperative mind: (?)
A monad is like a loop that can run a new
On 01/08/07, Andrew Wagner [EMAIL PROTECTED] wrote:
This seems wrong to me. A monad is, first and foremost, a type
constructor class. I'm not sure how you can really compare that to a
loop. But perhaps the easiest way to test your definition would be to
ask this: How is, for example, the Maybe
On 8/1/07, Andrew Wagner [EMAIL PROTECTED] wrote:
This seems wrong to me. A monad is, first and foremost, a type
constructor class. I'm not sure how you can really compare that to a
loop. But perhaps the easiest way to test your definition would be to
ask this: How is, for example, the Maybe
On 8/1/07, Andrew Wagner [EMAIL PROTECTED] wrote:
you can imagine each of the calls to putStrLn gets implicitly passed a
variable (here, the world ) and they happen in succession so it's
like a loop.
It breaks down further as soon as you add any amount of complexity to
the code as well.
On 8/1/07, david48 [EMAIL PROTECTED] wrote:
As a beginner haskeller coming from an imperative experience, I think
I understood what he meant.
say you have this code :
putStrLn 1 putStrLn 2 putStrLn 3
you can imagine each of the calls to putStrLn gets implicitly passed a
variable
say you have this code :
putStrLn 1 putStrLn 2 putStrLn 3
you can imagine each of the calls to putStrLn gets implicitly passed a
variable (here, the world ) and they happen in succession so it's
like a loop.
It breaks down further as soon as you add any amount of complexity to
the
Kaveh A monad is like a loop that can run a new function against its variable
in each iteration.
I’m an imperative programmer learning Haskell, so I’m a newbie, but I’ll give
it a try ☺ Making mistakes is the best way to learn it ;)
There are lots of different kinds of monads, but let’s stick
On 8/1/07, Andrew Wagner [EMAIL PROTECTED] wrote:
For me, I think the key to monads is to really
understand 2 things about them:
...
2.) Monads are about sequencing
Now I disagree on 2.
Monads are no more about sequencing than binary operators are about
sequencing. Sure, if you want to, you
an IO monad is a delayed action that will be executed as soon as that action
is needed for further evaluation of the program.
I'm not sure I like this, as it seems to confuse the issue. An expert
should correct me if I'm wrong, but monads in and of themselves don't
depend on laziness.
My own perspective on monads is this:
In procedural and OO languages, when dealing with compound data
structures, we think in terms of getters (*taking data out* of the
structure) and setters (*putting data in* to the structure).
Languages with some impure functional features (Lisp, Scheme,
Hello,
On 8/1/07, Andrew Wagner [EMAIL PROTECTED] wrote:
For me, I think the key to monads is to really
understand 2 things about them:
...
2.) Monads are about sequencing
Now I disagree on 2.
Monads are no more about sequencing than binary operators are about
sequencing. Sure, if
Kaveh A monad is like a loop that can run a new function against
its variable in each iteration.
I’m an imperative programmer learning Haskell, so I’m a newbie,
but I’ll give it a try ☺ Making mistakes is the best way to
learn it ;)
I was a newbie not so long ago so I can understand
Here's my rant about the way monads are explained in Haskell tutorials
(which are much too polluted with nuclear waste to be safely approached):
It is a big mistake to start with the IO monad. It pollutes and
misdirects the understanding of what a monad is. The dreaded nuclear
waste metaphor
Hello,
'Monad' is a type class.
So what's 'IO'? Is the correct terminology 'instance' as in 'IO is an
instance of Monad'. I consider 'IO' to be 'a monad' as that fits with
mathematical terminology.
I agree with this.
But what about an actual object of type 'IO
Int', say?
I usually
a Monad is a type constructor with two operations, implementing
a standard interface and following a few simple rules.
the Monad type class tells you the interface (what operations
you've got, and their types), the Monad laws tell you what all
types implementing that interface should have in
I knew someone was going to catch me wandering into the deep end of the
pool!
Having read large parts of your blog, I would never presume to tell you
anything about Haskell or category theory, but what the hell...
I mostly sympathise with your rant, but I think you need to be clearer
about
On Thursday 02 August 2007 08:17, Claus Reinke wrote:
a Monad is a type constructor with two operations, implementing
a standard interface and following a few simple rules.
. . . . and this is one of the best definitions i've seen yet. Thanks Claus!
i think we need to be looking at What is a
Someone asked about comparing monads to loops.
If you are chiefly familiar with the i/o and state monads, that doesn't
really make a lot of sense, but there IS a use of monads which IS a kind
of loop.
Only yesterday I was trying to read someone else's Haskell code where
they had imported
On 2 Aug 2007, at 5:13 am, alpheccar wrote:
I think the problem is due to a few bad tutorial still available on
the web and which are making two mistakes:
1 - Focusing on the IO monad which is very special ;
2 - Detailing the implementation. As a newie we don't care and we
would prefer to
On 2 Aug 2007, at 1:20 pm, Alexis Hazell wrote:
Category theorists can define monads concisely using the language
of their
discipline - surely we can settle on a definition of Haskell Monads
that
would make sense to any programmer who has mastered basic programming
concepts?
It all depends
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